1. Field of the Invention
The present invention relates to pigmented coatings, especially paints containing halogenated benzonitrile fungicide, and to a method for making such coatings.
2. Background of the Related Art
Biocides have been useful in various coating and paint formulations, such house paints, to prevent the growth of microorganisms such as bacteria, mold, and mildew. However, certain biocides can produce photochemical reactions upon exposure to ultraviolet (UV) radiation. This poses a problem especially for water-based exterior house paints, which are exposed to sunlight.
Halogenated benzonitrile based biocides, such as chlorothalonil, are effective at suppressing the growth of fungi, but present a problem in colored paints in that they lead to fading upon exposure to UV radiation. The fading is believed to be related to degradation of the binder, which produces chalking. Although the chalking can occur in light as well as dark colored paints, it is especially noticeable with dark or deeply hued pigments such as black, blue, etc. This problem precludes the use of halogenated benzonitrile based biocides in such paints.
What is needed is a way to incorporate halogenated benzonitrile based biocides in paint while having reduced fading.
The pigmented coatings described herein include a binder, a pigment, and a biocide containing from about 1% to about 99% by weight of a halogenated benzonitrile compound and from about 1% to about 99% by weight of a conazole compound.
Pigmented coatings with the combination of a conazole compound and a halogenated benzonitrile compound surprisingly exhibit less fading than pigmented coatings with only one type of biocide.
While the invention described herein may be used in conjunction with any type of coating material, it is especially useful for paints. In particular, the invention herein is especially useful for dark colored exterior paints such as used on houses. As used herein the term xe2x80x98darkxe2x80x99 shall refer to coatings having a reflectance of no more than about 25%.
As used herein the term xe2x80x98acrylicxe2x80x99 encompasses homopolymers and copolymers having unsubstituted or substituted acrylic moieties including acrylates, methacrylates, vinylacrylics, styrenated acrylics and the like.
A paint is a coating material including a solid pigment suspended in a liquid vehicle and which is applied to various surfaces. The pigment can be inorganic or organic. Inorganic pigments can be white or colored and can include, for example, titanium oxide, zinc oxide, chromium oxide, iron oxide, carbon black, and various combinations thereof. Organic pigments can include, for example, para-chlorinated nitroanilines, naphthol red, Hansa, benzidine, dinitroaniline orange, lithol, Persian orange, tartrazine, alizarine, indathrene, indigo blue, indigo maroon, phthalocyanine blue, phthalocyanine green, rhodamine, malachite green, methyl violet, and Victoria blue.
The vehicle typically includes a binder and, usually, a solvent or diluent such as water, mineral spirits, alcohols, ethers, ketones and esters. Various binders are known and commonly used such as alkyds, acrylics, vinyls, latex, and combinations thereof. Latex or emulsion paints typically use water as the diluent. The paint dries after application to the surface by evaporation of the diluent and/or hardening of the binder by chemical reaction. Other components may optionally also be incorporated into the paint formulation such as dispersing agents, defoamers, surfactants, driers, extenders, and the like.
The coating material herein includes, in addition to the pigment, binder, and other optional components, a biocide containing a blend of from about 1% to about 99% by weight of a halogenated benzonitrile compound and from about 1% to about 99% by weight of a conazole based compound, preferably from about 10% to about 90% by weight of the halogenated benzonitrile compound and from about 10% to about 90% by weight of the conazole compound, more preferably from about 20% to about 80% of the halogenated benzonitrile compound and from about 20% to about 80% of the conazole based fungicide, and most preferably about 40% to 60% of the halogenated benzonitrile compound and 40% to 60% of the conazole compound.
The halogenated benzonitrile preferably has the formula: 
wherein X1, X2, X3, X4 and X5 are hydrogen or halogen (Cl, F, Br, I) with at least one X being halogen, and n is equal to 0 or 1. A preferred di-cyano substituted halogenated benzene of formula (I) is tetrachloroisophthalonitrile, or xe2x80x98chlorothalonilxe2x80x99, which has the formula 
The conazole compound has a molecular formula including at least one benzene ring and a heterocyclic group having the structure 
The conazole compound can optionally be selected from tetraconazole, tebuconazole, hexaconazole, cyproconazole, penconazole, and flutriafol.
The biocide described herein is preferably used in a water-based acrylic paint. An exemplary composition for such paint is described below.
More particularly, the pigment of the preferred paint composition includes particles of organic or inorganic pigment, the various types of which are well known in the art and examples of which have been set forth above. A suitable pigment includes titanium oxide (TiO2) such as Ti-Pure(copyright) R-960 brand titania available from DuPont. Also useful are extenders such as Gold Bond(copyright) R brand silica (SiO2), available from Gold Bond. Moreover, various colorants can be added to provide different hues to the pigment. Such colorants are known in the art.
Acrylic binder can be provided in the form of an acrylic emulsion such as Rhoplex(copyright) AC-264 acrylic emulsion, available from Rohm and Haas Corp.
Desirable additives include primary pigment dispersants (e.g., Nopcosperse(copyright) 100 brand anionic polyelectrolyte, available from Henkel Corp.), co-dispersants (e.g., Triton(copyright) CF-10 brand surfactant, available from Union Carbide), defoaming agents (e.g., Foamaster(copyright) VL defoamer, available from Henkel Corp.), antifreeze agents (e.g., ethylene glycol, propylene glycol), thickeners (e.g., Natrosol(copyright) MHR brand hydroxyethyl cellulose, available from Hercules), rheology modifiers (e.g., Attagel(copyright) 50 brand clay, available from Englehart Co.), coalescing agents (e.g., Texanol(copyright) brand high molecular weight alcohol type coalescing agent, available from Eastman Chemicals), and bactericides (e.g., Nuosept(copyright) 95 brand in-can preservative, available from Hxc3xcls-Degussa).